1. Field of the Invention
This invention relates to Time Division Multiple (TDM), or Time Division Duplex (TDD), communication systems which utilize the CT2 standard (European Telecommunication Standard I-ETS, "Radio Equipment and System (RES); Common air interface specification to be used for the interworking between cordless telephone apparatus in the frequency band 864, 1 MHz, including public access service," November 1994) in particular. More particularly, this invention relates to a way of modifying a CT2 system to include "training" bits in the field normally reserved for the signaling channel of a TDM transmission or mux.
2. Discussion of Related Technology
The use of training bits is well known in the wireless communications art as a way to bring several aspects of a receiver to a steady state so information bits can be received correctly. In a TDM system, a gap of time typically occurs between one transmission burst and the next. For several reasons, a receiver may not be able to recall the exact parameters it used to receive the previous transmission burst, or, some parameters may have changed in the interim. For example, one parameter used is the slicing voltage level, i.e., that voltage above which is interpreted as a logic "1"and below which it is interpreted as a logic "0". It is common to turn power to the receiver off when it is not receiving and restore power when it is time to receive again. Although, this power management scheme reduces power consumption, it produces transients that disturb the receiver parameters. A receiver typically uses the first few bits, commonly known as "training" bits, to re-acquire these parameters to enable correct reception of the information bits.
Multiplex 2, Multiplex 1.2 and Multiplex 1.4 implemented by the CT2 standard, commonly referred to as MUX 2, MUX 1.2 and MUX 1.4 respectively, do not include the use of training bits. When the receiver is turned back on after the off power gap time, the first 16 bits (MUX 2), or the first bit (MUX 1.2), or the first two bits (MUX 1.4) convey the signaling channel and must be received correctly to avoid disrupting the communication channel. This adds difficulty to designing a TDD system based on the CT2 standard and can add undue cost to the radio demodulator design, since the signaling channel is used by a base station and handset, for example, to ascertain the status of the communication link and in communication exchange. If the signaling channel cannot be received due to errors, then this forces a link re-establishment to occur. If errors persist, the link is never established.